The present invention relates to the preparation of aluminoxanes, also known as polyhydrocarbylaluminoxanes. A preferred composition is polymethylaluminoxane. Polyhydrocarbylaluminoxanes are previously well-known in the art and are used as a component in the preparation of high activity homogenous Ziegler catalysts.
In Kaminsky, et. al. U.S. Pat. No. 4,544,762 there is disclosed a preparation of aluminoxanes employing the reaction between a hydrated aluminum salt and aluminum alkyls. Particularily desirable was the reaction between hydrated aluminum sulfate and aluminum trimethyl. The reaction is conducted in an inert solvent. For the teachings contained therein, the above identified patent is herein incorporated in its entirety by reference thereto.
EP 208,561 A2 discloses a similar process utilizing hydrated iron, magnesium, zinc and sodium salts. In each prior art process, the initial reagent was a trihydrocarbylaluminum compound. Despite advances in the art in the preparation of aluminoxanes, previously known processes have resulted in excessively long reaction times and an inability to recycle the metal salt employed therein. Moreover, such processes required tedious comminution of the hydrated salt in order to obtain selective control of the rate at which water is released to the reaction and thus control of the molecular weight and structure of the resulting aluminoxane compound.
It would be desirable if there were provided an improved process for the preparation of polyhydrocarbylaluminoxanes that would enable the skilled artisan to obtain improved efficiency.
In addition, it would be desirable to provide an improved process that would permit the facile regeneration of the hydrating agent.
It would also be desirable if there were provided a method allowing greater control of the release of water to the reaction mixture and an ability to utilize differing reactants, particularly lower grade or oligomeric aluminoxane materials such as are presently commercially available and to produce higher molecular weight materials therefrom.
Finally, it would be desirable if there were provided a continuous process for preparation of aluminoxane.